GASTROPODA. 883 
Bucania.] 
Specifically, A. costalis differs from K. esthona in the lesser prominence of the 
slit-band. A careless or inexperienced observer might confuse it with the associ- 
ated Tetranota bidorsata, yet any one accustomed to the work of discriminating 
between fossils can scarcely fail in separating them at once. 
Formation and locality.— Clitambonites bed of the Trenton group, near Cannon Falls, Minnesota. 
Collection.—B. O. Ulrich. 
Genus BUCANIA, Hall. 
Bucania (part.), HALL, 1847, Pal. New York, vol. i, p. 82. WAAGEN, 1880, Pal. Indica, ser. 13, pt. 2, 
pp. 180-150. Koxern, 1889, N. Jahrbuch f. Mineralogie, etc., Beilageband 
vi, p. 379. 
For generic characters see page 850. 
As originally defined by Hall, this genus was to include Pailereplontid shells 
having a large umbilicus. For many years the genus was regarded as of very 
doubtful value, paleontologists having learned that the relative size of the umbilicus 
was not of itself sufficient ground for a separate genus. The fact that the original 
types of Bucania had revolving lines was not considered of consequence by Hall in 
1847, nor by any other paleontologist who had occasion to refer to the bellerophon- 
tids previous to 1880. In this year an important work on these symmetrically 
involute shells was published by Waagen (op. cié.). This author proposed to apply 
the name Bucania to all bellerophontids possessing revolving striz, and he redefined 
the genus in accordance with his view. 
While it is not to be denied that Waagen’s proposal was a decided improvement 
upon previous attempts, it is still evident that his arrangement is artificial. His 
definition is too broad since it includes a variety of types that, while agreeing with 
the originals of Bucania in having spiral lines, are nevertheless widely removed from 
them genetically and readily distinguished by other characters. Lines of one kind 
or another, having a spiral direction, occur not only in species of the type of Bucania 
sulcatina, but in Salpingostoma and Tremanotus and in the new genera Cyrtolitina, 
Conradella and Tetranota. Then they occur in the very best development in a large 
group of species, ranging in time from the Trenton group to the close of the 
Paleozoic age, which we have decided to separate as a new genus under the name of 
Bucanopsis. 
The trouble with Bucania has been that its real peculiarities have never been 
appreciated. Hall, as stated, regarded the large open umbilicus as distinctive for 
the genus. His description says also that the mouth is abruptly expanded, but in 
this doubtless he was influenced by his B. expansa, which now is not a Bucania but a 
Salpingostoma. The name of the genus was most probably inspired by the same 
species, and ifit had been customary at that time to designate the type of a genus his 
